The present invention relates to a printer in an image processing apparatus such as a digital copying machine, facsimile, etc.
In general, in an image processing apparatus such as a copying machine, facsimile, etc. provided with a printer using laser beam, when image data are provided from an external equipment to the image processing apparatus, the external equipment starts to transmit the image data having one main scanning amount in synchronization with a horizontal synchronization signal outputted from the printer, and the transmission of the image data having the one main scanning amount is completed until the next horizontal synchronization signal is transmitted.
In accordance with such a construction of the image processing apparatus, the transmission of the image data is controlled on the printer side so that it is necessary for the external equipment to await the input of the horizontal synchronization signal from the printer when the image data are outputted.
Further, it is necessary to dispose a means for adjusting the timing of the output of the image data to connect such printers in parallel to each other by providing a buffer memory for every printer, etc., since the respective printers are not operated in synchronization with each other. In an apparatus disclosed in Japanese Laid-Open Patent No. 62-242909 for example, to synchronize a plurality of rotary polygon mirrors with each other, a control signal is supplied from a common means for generating a frequency signal to a PLL circuit for controlling a drive motor for driving the respective rotary polygon mirrors. However, such an apparatus does not provide any solution about the problems with respect to the transmission of the image data.
The above-mentioned problem is that the external equipment connected to the printer has no information about write scanning speed of the printer, i.e., the rotary speed and the number of mirror faces of deflectors or rotary polygon mirrors. If the time interval in transfer of the image data on one line in the external equipment is shorter than that in the horizontal synchronization signal, the image data on the next line are transferred before the data amount on the one line has been completely written on the printer side so that the printer cannot correspond to these image data.
To correspond to such a situation on the printer side, it is necessary for the printer to have a large amount of buffer memories. Such a large amount of memories must be prepared when the image data on a plurality of pages are transferred.
Japanese published patent No. 62-60870 discloses an apparatus in which a signal for driving the printer is externally supplied. However, in this apparatus, the speed of the printer in a secondary scanning direction is controlled in accordance with the amount of image data, but there is no means for recording or writing out the image data in the main scanning direction.